Isolation rectification voltage regulation circuit with active absorption and low-voltage DC power supply system

Abstract

The invention discloses an isolation, rectification and voltage regulation circuit with active absorption and a low-voltage direct-current power supply system. The isolation, rectification and voltage regulation circuit comprises a transformer, a first chopping unit and a second chopping unit, the transformer is provided with a first winding arranged on the primary side, and a second winding and a third winding which are arranged on the secondary side, the first chopping unit is arranged to be of a full-wave rectification structure and is connected with the second winding and the third winding, and the second chopping unit is arranged to be of a step-down circuit structure and is connected with the first chopping unit; a first capacitor is arranged on a branch where the first chopping unit is connected with the second winding, a second capacitor is arranged on a branch where the first chopping unit is connected with the third winding, and the first capacitor and the second capacitor can restrain voltage stress on switching tubes in the first chopping unit and the second chopping unit. Compared with the prior art, a resistor does not need to be used for suppressing the charge and discharge current of the absorption capacitor, the cost can be further reduced, and the efficiency is optimized.

Description

Technical Field

[0001] The present invention relates to the field of new energy vehicles, and in particular to an isolated rectifier voltage regulating circuit with active absorption and a low-voltage direct current power supply system. Background Art

[0002] With the continuous development of the new energy vehicle industry, the requirements for the power, efficiency and voltage range of low-voltage DC power supply systems are getting higher and higher. Traditional isolated rectifier circuits, such as full-bridge rectifier circuits, full-wave rectifier circuits, and half-wave rectifier circuits, can only convert AC voltage into DC voltage, but cannot achieve voltage regulation. At the same time, due to the increase in power, the influence of the leakage inductance of the transformer and the parasitic inductance on the line are becoming more and more obvious, causing oscillations between devices and causing stress problems. The traditional RCD absorption circuit absorbs the energy of the leakage inductance that generates voltage spikes in the capacitor, and then consumes it in the form of heat through the resistor, which not only increases more devices and costs, but also reduces efficiency. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention proposes an isolated rectifier voltage regulating circuit with active absorption and a low-voltage direct current power supply system.

[0004] The technical solution of the present invention is to propose an isolated rectifier voltage regulating circuit with active absorption, comprising a transformer, a first chopper unit, and a second chopper unit;

[0005] The transformer comprises a first winding arranged on the primary side, and a second winding and a third winding arranged on the secondary side, the first chopper unit is arranged as a full-wave rectification structure and is connected to the second winding and the third winding, and the second chopper unit is arranged as a step-down circuit structure and is connected to the first chopper unit;

[0006] A first capacitor is provided in a branch connecting the first chopping unit and the second winding, and a second capacitor is provided in a branch connecting the first chopping unit and the third winding. The first capacitor and the second capacitor can suppress the voltage stress on the switching tubes in the first chopping unit and the second chopping unit.

[0007] Furthermore, the first chopping unit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first capacitor, and a second capacitor;

[0008] The first switch tube is connected in series with the second winding, and the first end of the first switch tube is connected to the opposite end of the second winding, and the first capacitor is connected in series with the second switch tube and then connected in parallel to the two ends of the first switch tube;

[0009] The third switch tube is connected in series with the third winding, and the first end of the third switch tube is connected to the same-name end of the third winding. The second capacitor is connected in series with the fourth switch tube and then connected in parallel to the two ends of the third switch tube.

[0010] Further, the second chopping unit includes: a fifth switch tube, a sixth switch tube, a first inductor, and a third capacitor;

[0011] The first end of the fifth switch tube is respectively connected to the same-name end of the second winding and the opposite-name end of the third winding, the second end of the fifth switch tube is connected in series with the first inductor and then connected to the first end of the third capacitor, and the second end of the third capacitor is respectively connected between the second end of the first switch tube and the first capacitor, and between the second end of the third switch tube and the second capacitor;

[0012] The first end of the sixth switch tube is connected between the second end of the fifth switch tube and the first inductor, and the second end of the sixth switch tube is connected to the second end of the third capacitor.

[0013] Furthermore, it also includes at least one diode connecting the first chopping unit and the second chopping unit;

[0014] When the diode is set to one, the anode of the diode is connected to the first end of the fifth switch tube, and the cathode of the diode is connected between the second switch tube and the first capacitor;

[0015] Or the anode of the diode is connected to the first end of the fifth switch tube, and the cathode of the diode is connected between the fourth switch tube and the second capacitor.

[0016] Further, when there are two diodes, namely a first diode and a second diode, the anode of the first diode is connected to the first end of the fifth switch tube, and the cathode of the first diode is connected between the second switch tube and the first capacitor;

[0017] The anode of the second diode is connected to the first end of the fifth switch tube, and the cathode of the second diode is connected between the fourth switch tube and the second capacitor.

[0018] Furthermore, the isolated rectifier and voltage regulator circuit with active absorption has a slow-start phase and a steady-state phase. When the input voltage pulse width or amplitude on the primary side is not fully established, the isolated rectifier and voltage regulator circuit with active absorption operates in the slow-start phase.

[0019] When the input voltage pulse width and amplitude on the primary side are fully established, the isolated rectifier and voltage regulator circuit with active absorption operates in a steady-state stage.

[0020] Furthermore, when the isolated rectifier voltage regulator circuit with active absorption operates in the slow-start stage, the control timing of the first switch tube is the same as that of the fourth switch tube, the control timing of the second switch tube is the same as that of the third switch tube, and the control timing of the first switch tube differs from that of the second switch tube by 180°;

[0021] When the input voltage on the primary side is positive, the first switch tube and the fourth switch tube are turned on after the rising edge of the input voltage, the first switch tube and the fourth switch tube are turned off before the falling edge of the input voltage, and the fifth switch tube is turned off before the rising edge of the input voltage;

[0022] When the input voltage on the primary side is negative, the second switch tube and the third switch tube are turned on after a falling edge of the input voltage, the second switch tube and the third switch tube are turned off before a rising edge of the input voltage, and the fifth switch tube is turned off before a falling edge of the input voltage;

[0023] The control timings of the fifth switch tube and the sixth switch tube are complementary, and the switching frequency is twice that of the first switch tube.

[0024] Furthermore, when the isolated rectifier and voltage regulator circuit with active absorption operates in a steady-state stage, the control timings of the first switch tube and the second switch tube are complementary, the control timings of the third switch tube and the fourth switch tube are complementary, and the control timings of the first switch tube and the third switch tube differ by 180°;

[0025] When the input voltage on the primary side is positive, the third switch tube is turned off before the rising edge of the input voltage, the third switch tube is turned on after the falling edge of the input voltage, the fourth switch tube is turned on after the rising edge of the input voltage, the fourth switch tube is turned off before the rising edge of the input voltage, and the fifth switch tube is turned off before the rising edge of the input voltage;

[0026] When the input voltage of the primary side is negative, the first switch tube is turned on after the rising edge of the input voltage, the first switch tube is turned off before the falling edge of the input voltage, the second switch tube is turned off before the rising edge of the input voltage, the second switch tube is turned on after the falling edge of the input voltage, and the fifth switch tube is turned off before the falling edge of the input voltage;

[0027] The control timings of the fifth switch tube and the sixth switch tube are complementary, and the switching frequency is twice that of the second switch tube.

[0028] Furthermore, the minimum capacity of the first capacitor and the second capacitor is:

[0029]

[0030] Among them, L k is the leakage inductance, L b is the parasitic inductance, I max is the maximum value of the current flowing from the first chopper unit to the second chopper unit, V max is the expected maximum voltage stress of the first switch tube and the third switch tube, V1 max is the peak value of the input voltage on the primary side.

[0031] The present invention also proposes a low-voltage direct current power supply system, which has the above-mentioned isolated rectifying and voltage regulating circuit with active absorption.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] The present invention realizes the functions of rectification and voltage regulation simultaneously by cascading a full-wave rectifier circuit and a buck circuit. On this basis, the voltage stress suppression of the synchronous rectifier tube of the full-wave rectifier circuit and the switch tube of the buck circuit is simultaneously realized through a shared capacitor, and the absorption capacitor is discharged at a suitable working stage through timing control to maintain good stress suppression capability. The present invention does not need to use a resistor to suppress the charging and discharging current of the absorption capacitor, the cost can be further reduced, and the efficiency is optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 The circuit topology diagram of the isolated rectifier voltage regulator circuit with active absorption of the present invention;

[0036] Figure 2 This is a control timing diagram of each switch tube in the slow start stage of the present invention;

[0037] Figure 3 This is a control timing diagram of each switch tube in the steady state stage of the present invention. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] Thus, a feature indicated in this specification will be used to illustrate one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although some features can be combined together to illustrate possible system designs, these features can also be used in other combinations that are not explicitly described. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

[0040] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0041] In view of the problems raised in the prior art, the present invention proposes an isolated rectifier voltage regulating circuit with active absorption, which includes a transformer, a first chopper unit, and a second chopper unit;

[0042] The transformer has a first winding N1 arranged on the primary side, and a second winding N2 and a third winding N3 arranged on the secondary side, the first chopper unit is arranged as a full-wave rectification structure and is connected to the second winding N2 and the third winding N3, the second chopper unit is arranged as a step-down circuit structure and is connected to the first chopper unit;

[0043] A first capacitor C1 is provided in a branch connecting the first chopping unit and the second winding N2, and a second capacitor C2 is provided in a branch connecting the first chopping unit and the third winding N3. The first capacitor C1 and the second capacitor C2 can suppress the voltage stress on the switch tubes in the first chopping unit and the second chopping unit.

[0044] Here, the main function of the full-wave rectifier structure is to achieve rectification, and the main function of the buck circuit is to achieve voltage regulation. The present invention cascades the above-mentioned full-wave rectifier circuit and the buck circuit, which can achieve rectification and voltage regulation functions at the same time.

[0045] In addition, the first capacitor C1 and the second capacitor C2 are used as absorption capacitors to suppress the voltage stress of the synchronous rectifier tube in the synchronous rectifier circuit and the switch tube in the buck circuit. At the same time, with the corresponding control timing, the electric energy absorbed by the first capacitor C1 and the second capacitor C2 is discharged at the appropriate working stage, which can maintain good stress suppression capability.

[0046] Compared with the conventional solution of using a resistor to charge and discharge the absorption capacitor, the cost of the present invention can be further reduced, and the efficiency of the entire system is also optimized.

[0047] The specific circuit topology of the isolated rectifier and voltage regulator circuit with active absorption in the present invention is described below in conjunction with the accompanying drawings, with reference to the first chopper unit:

[0048] See also Figure 1 In the present invention, the first chopping unit includes: a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a first capacitor C1, and a second capacitor C2;

[0049] The first switch tube S1 is connected in series with the second winding N2, and the first end of the first switch tube S1 is connected to the opposite end of the second winding N2. The first capacitor C1 is connected in series with the second switch tube S2 and then connected in parallel to both ends of the first switch tube S1.

[0050] The third switch tube S3 is connected in series with the third winding N3, and the first end of the third switch tube S3 is connected to the same end of the third winding N3. The second capacitor C2 is connected in series with the fourth switch tube S4 and then connected in parallel to both ends of the third switch tube S3.

[0051] Here, the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 form a full-wave rectification circuit, which can realize the rectification function of the circuit by adjusting the on-off state of the above switch tubes.

[0052] For the second chopper unit:

[0053] See also Figure 1 , the second chopping unit in the present invention includes: a fifth switch tube S5, a sixth switch tube S6, a first inductor L, and a third capacitor C3;

[0054] The first end of the fifth switch tube S5 is respectively connected to the same-name end of the second winding N2 and the opposite-name end of the third winding N3, the second end of the fifth switch tube S5 is connected in series with the first inductor L and then connected to the first end of the third capacitor C3, the second end of the third capacitor C3 is respectively connected between the second end of the first switch tube S1 and the first capacitor C1, and between the second end of the third switch tube S3 and the second capacitor C2;

[0055] A first end of the sixth switch tube S6 is connected between the second end of the fifth switch tube S5 and the first inductor L, and a second end of the sixth switch tube S6 is connected to the second end of the third capacitor C3.

[0056] The second chopping unit forms a step-down circuit structure through the fifth switch tube S5, the sixth switch tube S6, the inductor L and the third capacitor C3, wherein the first side, i.e., the side connected to the first chopping unit, is the input, and the second side, i.e., the side where the third capacitor C3 is set, is the output. After passing through the second chopping unit, the input voltage on the first side can be raised and output through the second side.

[0057] Furthermore, in the present invention, at least one diode D is connected between the first chopping unit and the second chopping unit, wherein when the number of the diode D is set to one, the anode of the diode D is connected to the first end of the fifth switch tube S5, and the cathode of the diode D is connected between the second switch tube S2 and the first capacitor C1;

[0058] Or the anode of the diode D is connected to the first end of the fifth switch tube S5, and the cathode of the diode D is connected between the fourth switch tube S4 and the second capacitor C2.

[0059] See also Figure 1 , which is a solution in which the above-mentioned diode D is set as one, the cathode of the diode D is connected between the fourth switch tube S4 and the second capacitor C2, and the anode is connected to the first end of the fifth switch tube S5;

[0060] In other embodiments of the present invention, two diodes may be provided at the same time, which may have the same technical effect. Specifically, when two diodes are provided, namely, a first diode D1 and a second diode D2, the anode of the first diode D1 is connected to the first end of the fifth switch tube S5, and the cathode of the first diode D1 is connected between the second switch tube S2 and the first capacitor C1.

[0061] The anode of the second diode D2 is connected to the first end of the fifth switch tube S5 , and the cathode of the second diode D2 is connected between the fourth switch tube S4 and the second capacitor C2 .

[0062] Further, based on the above circuit topology, the isolated rectifier voltage regulator circuit with active absorption in the present invention includes two working stages, namely a slow start stage and a steady state stage. When the pulse width or amplitude of the input voltage V1 on the primary side is not fully established, the isolated rectifier voltage regulator circuit with active absorption works in the slow start stage to prevent the output voltage V2 on the secondary side from being fed back;

[0063] When the pulse width and amplitude of the input voltage V1 on the primary side are fully established, the isolated rectifier and voltage regulator circuit with active absorption operates in a steady-state stage, which is used to improve the working efficiency of the isolated rectifier and voltage regulator circuit with active absorption.

[0064] When the isolated rectifier voltage regulator circuit with active absorption works in the slow start stage, the control timing of the first switch tube S1 and the fourth switch tube S4 is the same, the control timing of the second switch tube S2 and the third switch tube S3 is the same, and the control timing of the first switch tube S1 and the second switch tube S2 differs by 180°;

[0065] When the input voltage V1 on the primary side is positive, the first switch tube S1 and the fourth switch tube S4 are turned on after the rising edge of the input voltage V1, the first switch tube S1 and the fourth switch tube S4 are turned off before the falling edge of the input voltage V1, and the fifth switch tube S5 is turned off before the rising edge of the input voltage V1;

[0066] When the input voltage V1 on the primary side is negative, the second switch tube S2 and the third switch tube S3 are turned on after the falling edge of the input voltage V1, the second switch tube S2 and the third switch tube S3 are turned off before the rising edge of the input voltage V1, and the fifth switch tube S5 is turned off before the falling edge of the input voltage V1;

[0067] The control timings of the fifth switch tube S5 and the sixth switch tube S6 are complementary, and the switching frequency is twice that of the first switch tube S1.

[0068] like Figure 2 As shown, the first switch tube S1 and the fourth switch tube S4 are turned on and off at the same time, the second switch tube S2 and the third switch tube S3 are turned on and off at the same time, the first switch tube S1 and the fourth switch tube S4 are staggered 180° with the second switch tube S2 and the third switch tube S3, the switching frequency is the first switching frequency fs1, and the duty cycle is the first duty cycle Duty1 and is less than 0.5.

[0069] When the voltage V1 across the first winding N1 of the transformer T is positive, the first switch tube S1 and the fourth switch tube S4 are turned on after the rising edge of V1 by the time t, and the first switch tube S1 and the fourth switch tube S4 are turned off before the falling edge of V1 by the time t;

[0070] When the voltage V1 across the first winding N1 of the transformer T is negative, the second switch tube S2 and the third switch tube S3 are turned on after the falling edge of V1 by the time t, and the second switch tube S2 and the third switch tube S3 are turned off before the rising edge of V1 by the time t;

[0071] The fifth switch tube S5 and the sixth switch tube S6 are complementary, and their switching frequencies are the second switching frequency fs2, where fs2 = 2*fs1.

[0072] When the voltage V1 across the first winding N1 of the transformer T is positive, the fifth switch tube S5 is turned off before the rising edge of V1 by time t; when V1 is negative, the fifth switch tube S5 is turned off before the falling edge of V1 by time t; the turn-on time of the fifth switch tube S5 is not fixed, but is determined by the second duty cycle Duty2, and the turn-on time is ahead of the turn-off time Duty2 / fs2 of the fifth switch tube S5.

[0073] When the isolated rectifier and voltage regulator circuit with active absorption operates in a steady state, the control timings of the first switch tube S1 and the second switch tube S2 are complementary, the control timings of the third switch tube S3 and the fourth switch tube S4 are complementary, and the control timings of the first switch tube S1 and the third switch tube S3 differ by 180°;

[0074] When the input voltage V1 on the primary side is positive, the third switch tube S3 is turned off before the rising edge of the input voltage V1, and the third switch tube S3 is turned on after the falling edge of the input voltage V1, the fourth switch tube S4 is turned on after the rising edge of the input voltage V1, the third switch tube S3 is turned on after the falling edge of the input voltage V1, the fourth switch tube S4 is turned off before the rising edge of the input voltage V1, and the fifth switch tube S5 is turned off before the rising edge of the input voltage V1;

[0075] When the input voltage V1 on the primary side is negative, the first switch tube S1 is turned on after the rising edge of the input voltage V1, the first switch tube S1 is turned off before the falling edge of the input voltage V1, the second switch tube S2 is turned off before the rising edge of the input voltage V1, the second switch tube S2 is turned on after the falling edge of the input voltage V1, and the fifth switch tube S5 is turned off before the falling edge of the input voltage V1;

[0076] The control timings of the fifth switch tube S5 and the sixth switch tube S6 are complementary, and the switching frequency is twice that of the second switch tube S2.

[0077] like Figure 3 As shown, the first switch tube S1 is complementary to the second switch tube S2, the third switch tube S3 is complementary to the fourth switch tube S4, the first switch tube S1 and the third switch tube S3 are staggered by 180°, the switching frequency is the first switching frequency fs1, and the duty cycle is the first duty cycle Duty1 and is greater than 0.5.

[0078] When the voltage V1 across the first winding N1 of the transformer T is negative, the first switch S1 is turned off before the falling edge of V1 by time t, and the second switch S2 is turned on after time t; the first switch S1 is turned on after time t of the rising edge of V1, and the second switch S2 is turned off before time t;

[0079] When the voltage V1 across the first winding N1 of the transformer T is positive, the third switch tube S3 is turned off before the rising edge of V1 by time t, and the fourth switch tube S4 is turned on after time t; the third switch tube S3 is turned on after time t at the falling edge of V1, and the fourth switch tube S4 is turned off before time t.

[0080] The fifth switch tube S5 and the sixth switch tube S6 are complementary, and their switching frequencies are the second switching frequency fs2, where fs2 = 2*fs1.

[0081] When the voltage V1 across the first winding N1 of the transformer T is positive, the fifth switch tube S5 is turned off before the rising edge of V1 by time t;

[0082] When the voltage V1 across the first winding N1 of the transformer T is negative, the fifth switch tube S5 is turned off before the falling edge of V1 by time t;

[0083] The turn-on time of the fifth switch tube S5 is not fixed, but is determined by the second duty cycle Duty2, and the turn-on time is ahead of the turn-off time Duty2 / fs2 of the fifth switch tube S5.

[0084] The overall operation process of the present invention is described below.

[0085] Time t is the dead time and is greater than 0.

[0086] When V1 is positive, energy flows to the first side of the second chopper unit through the first switch tube S1;

[0087] When V2 is negative, energy flows to the first side of the second chopper unit through the third switch tube S3.

[0088] When the fifth switch tube S5 is turned on, energy flows from the first side to the second side of the second chopping unit.

[0089] The energy flowing from V1 to V2 is determined by the second duty cycle Duty2, which ranges from 0 to 1. It is particularly noted that when the second duty cycle Duty2 is equal to 0, the fifth switch tube S5 is normally closed; when the second duty cycle Duty2 is equal to 1, the fifth switch tube S5 is normally open.

[0090] When V1 drops from positive to 0V, the leakage inductance energy of the second winding N2 is absorbed by the first capacitor C1 through the body diode of the second switch tube S2; when V1 rises from negative to 0V, the leakage inductance energy of the third winding N3 is absorbed by the second capacitor C2 through the body diode of the fourth switch tube S4; when the fifth switch tube S5 is turned off, the parasitic inductance energy on the line from the center tap of the second winding N2 and the third winding N3 to the fifth switch tube S5 is absorbed by the second capacitor C2 through the diode D.

[0091] When the first switch tube S1 and the fourth switch tube S4 are turned on, the energy stored in the second capacitor C2 is released through the fourth switch tube S4, the third winding N3, the second winding N2, and the first switch tube S1 until the voltage of the second capacitor C2 is approximately equal to Vs1+Vs2;

[0092] When the second switch tube S2 and the third switch tube S3 are turned on, the energy stored in the first capacitor C1 is released through the second switch tube S2, the second winding N2, the third winding N3, and the third switch tube S3 until the voltage of the first capacitor C1 is approximately equal to Vs1+Vs2.

[0093] Through the absorption and release of the first capacitor C1 and the second capacitor C2, the voltage stress of the first switch tube S1, the third switch tube S3 and the fifth switch tube S5 can be effectively suppressed to prevent failure due to exceeding the withstand voltage value of the device.

[0094] Furthermore, the minimum capacity of the first capacitor C1 and the second capacitor C2 in the present invention is:

[0095]

[0096] Among them, L k is the leakage inductance, L b is the parasitic inductance, I max is the maximum value of the current from the first chopper unit to the second chopper unit, V max is the expected maximum voltage stress of the first switch tube and the third switch tube, V1 max is the peak value of the input voltage on the primary side.

[0097] The derivation process is:

[0098] The maximum value of energy released by leakage inductance and parasitic inductance is:

[0099] The energy that can be absorbed by the first capacitor C1 or the second capacitor C2 is:

[0100] Therefore, the minimum capacitance required for the first capacitor C1 and the second capacitor C2 is:

[0101] Furthermore, the present invention also proposes a low-voltage direct current power supply system, which has the above-mentioned isolated rectification and voltage regulation circuit with active absorption.

[0102] Compared with the prior art, the present invention has at least the following beneficial effects:

[0103] The present invention realizes the functions of rectification and voltage regulation simultaneously by cascading a full-wave rectifier circuit and a buck circuit. On this basis, the voltage stress suppression of the synchronous rectifier tube of the full-wave rectifier circuit and the switch tube of the buck circuit is simultaneously realized through a shared capacitor, and the absorption capacitor is discharged at a suitable working stage through timing control to maintain good stress suppression capability. The present invention does not need to use a resistor to suppress the charging and discharging current of the absorption capacitor, the cost can be further reduced, and the efficiency is optimized.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An isolated rectifier and voltage regulator circuit with active absorption, characterized in that: It includes a transformer, a first chopping unit, and a second chopping unit; The transformer comprises a first winding arranged on the primary side, and a second winding and a third winding arranged on the secondary side, the first chopper unit is arranged as a full-wave rectification structure and is connected to the second winding and the third winding, and the second chopper unit is arranged as a step-down circuit structure and is connected to the first chopper unit; A first capacitor is provided in a branch connecting the first chopping unit and the second winding, and a second capacitor is provided in a branch connecting the first chopping unit and the third winding. The first capacitor and the second capacitor can suppress the voltage stress on the switching tubes in the first chopping unit and the second chopping unit.

2. The isolated rectifier and voltage regulator circuit with active absorption according to claim 1, characterized in that: The first chopping unit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first capacitor, and a second capacitor; The first switch tube is connected in series with the second winding, and the first end of the first switch tube is connected to the opposite end of the second winding, and the first capacitor is connected in series with the second switch tube and then connected in parallel to the two ends of the first switch tube; The third switch tube is connected in series with the third winding, and the first end of the third switch tube is connected to the same-name end of the third winding. The second capacitor is connected in series with the fourth switch tube and then connected in parallel to the two ends of the third switch tube.

3. The isolated rectifier and voltage regulator circuit with active absorption according to claim 2, characterized in that: The second chopping unit includes: a fifth switch tube, a sixth switch tube, a first inductor, and a third capacitor; The first end of the fifth switch tube is respectively connected to the same-name end of the second winding and the opposite-name end of the third winding, the second end of the fifth switch tube is connected in series with the first inductor and then connected to the first end of the third capacitor, and the second end of the third capacitor is respectively connected between the second end of the first switch tube and the first capacitor, and between the second end of the third switch tube and the second capacitor; The first end of the sixth switch tube is connected between the second end of the fifth switch tube and the first inductor, and the second end of the sixth switch tube is connected to the second end of the third capacitor.

4. The isolated rectifier and voltage regulator circuit with active absorption according to claim 3, characterized in that: Also comprising at least one diode connecting the first chopping unit and the second chopping unit; When the diode is set to one, the anode of the diode is connected to the first end of the fifth switch tube, and the cathode of the diode is connected between the second switch tube and the first capacitor; Or the anode of the diode is connected to the first end of the fifth switch tube, and the cathode of the diode is connected between the fourth switch tube and the second capacitor.

5. The isolated rectifier and voltage regulator circuit with active absorption according to claim 4, characterized in that: When there are two diodes, namely a first diode and a second diode, the anode of the first diode is connected to the first end of the fifth switch tube, and the cathode of the first diode is connected between the second switch tube and the first capacitor; The anode of the second diode is connected to the first end of the fifth switch tube, and the cathode of the second diode is connected between the fourth switch tube and the second capacitor.

6. The isolated rectifier and voltage regulator circuit with active absorption according to claim 3, characterized in that: The isolated rectifier and voltage regulator circuit with active absorption has a slow-start phase and a steady-state phase. When the input voltage pulse width or amplitude of the primary side is not fully established, the isolated rectifier and voltage regulator circuit with active absorption operates in the slow-start phase; When the input voltage pulse width and amplitude on the primary side are fully established, the isolated rectifier and voltage regulator circuit with active absorption operates in a steady-state stage.

7. The isolated rectifier and voltage regulator circuit with active absorption according to claim 6, characterized in that: When the isolated rectifier voltage regulator circuit with active absorption operates in the slow start stage, the control timing of the first switch tube is the same as that of the fourth switch tube, the control timing of the second switch tube is the same as that of the third switch tube, and the control timing of the first switch tube differs from that of the second switch tube by 180°; When the input voltage on the primary side is positive, the first switch tube and the fourth switch tube are turned on after the rising edge of the input voltage, the first switch tube and the fourth switch tube are turned off before the falling edge of the input voltage, and the fifth switch tube is turned off before the rising edge of the input voltage; When the input voltage on the primary side is negative, the second switch tube and the third switch tube are turned on after a falling edge of the input voltage, the second switch tube and the third switch tube are turned off before a rising edge of the input voltage, and the fifth switch tube is turned off before a falling edge of the input voltage; The control timings of the fifth switch tube and the sixth switch tube are complementary, and the switching frequency is twice that of the first switch tube.

8. The isolated rectifier and voltage regulator circuit with active absorption according to claim 6, characterized in that: When the isolated rectifier and voltage regulator circuit with active absorption operates in a steady-state stage, the control timings of the first switch tube and the second switch tube are complementary, the control timings of the third switch tube and the fourth switch tube are complementary, and the control timings of the first switch tube and the third switch tube differ by 180°; When the input voltage on the primary side is positive, the third switch tube is turned off before the rising edge of the input voltage, the third switch tube is turned on after the falling edge of the input voltage, the fourth switch tube is turned on after the rising edge of the input voltage, the fourth switch tube is turned off before the rising edge of the input voltage, and the fifth switch tube is turned off before the rising edge of the input voltage; When the input voltage of the primary side is negative, the first switch tube is turned on after the rising edge of the input voltage, the first switch tube is turned off before the falling edge of the input voltage, the second switch tube is turned off before the rising edge of the input voltage, the second switch tube is turned on after the falling edge of the input voltage, and the fifth switch tube is turned off before the falling edge of the input voltage; The control timings of the fifth switch tube and the sixth switch tube are complementary, and the switching frequency is twice that of the second switch tube.

9. The isolated rectifier and voltage regulator circuit with active absorption according to claim 2, characterized in that: The minimum capacity of the first capacitor and the second capacitor is: Among them, L k is the leakage inductance, L b is the parasitic inductance, I max is the maximum value of the current flowing from the first chopper unit to the second chopper unit, V max is the expected maximum voltage stress of the first switch tube and the third switch tube, V1 max is the peak value of the input voltage on the primary side.

10. A low voltage DC power supply system, characterized in that: The low-voltage DC power supply system has an isolated rectifier and voltage regulator circuit with active absorption as claimed in any one of claims 1 to 9.

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